#!/usr/bin/env bash

set -eo pipefail


function usage() {
  cat > /dev/stdout <<EOF
Usage: run_docker [OPTIONS] [COMMAND] [ARG...]

Runs COMMAND in a new Pyodide docker container. If no COMMAND is provided, starts a bash
shell in the container.

Options:
  -h, --help                  Show this information and exit.
  --pre-built                 Use the prebuilt Pyodide image.
                              This is ignored if the env var PYODIDE_DOCKER_IMAGE is set.
  -p, --port <port>           System port to which to forward.
                              This is ignored if the env var PYODIDE_SYSTEM_PORT is set.
                              If set to 'none', docker instance will not bind to any port.

Prerequisites:
  Docker has to be set up on your system.
EOF
}

function error() {
  usage
  exit 255
}


PYODIDE_IMAGE_TAG="15"
PYODIDE_PREBUILT_IMAGE_TAG="0.17.0"
DEFAULT_PYODIDE_DOCKER_IMAGE="pyodide/pyodide-env:${PYODIDE_IMAGE_TAG}"
DEFAULT_PYODIDE_SYSTEM_PORT="8000"
DOCKER_COMMAND="/bin/bash"

while [[ $# -gt 0 ]]
do
  key="$1"
  case $key in
      -h|--help)
        usage
        exit 0
      ;;
      --pre-built)
        if [[ -n ${PYODIDE_DOCKER_IMAGE} ]]; then
          echo "WARNING: will use the env var PYODIDE_DOCKER_IMAGE=${PYODIDE_DOCKER_IMAGE},
          the flag --pre-built has no effect"
        fi
        DEFAULT_PYODIDE_DOCKER_IMAGE="pyodide/pyodide:${PYODIDE_PREBUILT_IMAGE_TAG}"
        shift
      ;;
      -p|--port)
        if [ "$#" -lt 2 ]; then
          >&2 echo "port cannot be empty"
          error
        fi
        if [[ -n ${PYODIDE_SYSTEM_PORT} ]]; then
          echo "WARNING: will use the env var PYODIDE_SYSTEM_PORT=${PYODIDE_SYSTEM_PORT} instead of the provided port"
        fi
        DEFAULT_PYODIDE_SYSTEM_PORT=$2
        shift 2
      ;;
      -*)
        >&2 echo "Unknown option $1"
        error
      ;;
      *)
        DOCKER_COMMAND="$@"
        break
      ;;
  esac
done

PYODIDE_DOCKER_PORT=${PYODIDE_DOCKER_PORT:-"8000"}
PYODIDE_SYSTEM_PORT=${PYODIDE_SYSTEM_PORT:-${DEFAULT_PYODIDE_SYSTEM_PORT}}
PYODIDE_DOCKER_IMAGE=${PYODIDE_DOCKER_IMAGE:-${DEFAULT_PYODIDE_DOCKER_IMAGE}}

# in case the port is not a number, do not bind the port
case $DEFAULT_PYODIDE_SYSTEM_PORT in
  none)
  PORT_CONFIGURATION_LINE=""
  ;;
  ''|*[!0-9]*) # contains a non-digit character, therefore it is not a number
  echo "WARNING: Invalid port argument '$DEFAULT_PYODIDE_SYSTEM_PORT'. Port binding disabled."
  PORT_CONFIGURATION_LINE=""
  ;;
  *)
  PORT_CONFIGURATION_LINE="-p $PYODIDE_SYSTEM_PORT:$PYODIDE_DOCKER_PORT"
  ;;
esac

mkdir -p .docker_home

USER_HOME="/src/.docker_home"
USER_NAME="$(id -u -n)"
USER_PASS="x"
USER_ID="$(id -u)"
USER_GID=0
USER_COMMENT_FIELD="${USER_NAME} pyodide user alias"
USER_INTERPRETER="/sbin/nologin"
USER_ACCOUNT_INFO="${USER_NAME}:${USER_PASS}:${USER_ID}:${USER_GID}:${USER_COMMENT_FIELD}:${USER_HOME}:${USER_INTERPRETER}"

# Start a detached container as root, add the host uname and uid to /etc/passwd,
# then run forever
CONTAINER=$(\
  docker run \
    -d --rm \
    -v $PWD:/src \
    --user root \
    --shm-size 2g \
    "${PYODIDE_DOCKER_IMAGE}" \
    /bin/bash -c " \
      echo '${USER_ACCOUNT_INFO}' >> /etc/passwd ; \
      tail -f /dev/null \
    " \
)

EXIT_STATUS=0
# Execute the provided command as the host user with HOME=/src
docker exec \
  -it \
  --user $(id --user):$(id --group) \
  $CONTAINER \
  /bin/bash -c "${DOCKER_COMMAND}" || EXIT_STATUS=$?

docker kill $CONTAINER > /dev/null
exit $EXIT_STATUS
